1. Field of the Invention
This invention relates to a process for obtaining acrylamide or methacrylamide as a stable aqueous solution without polymerization in producing acrylamide or methacrylamide using microorganisms.
2. Description of Prior Art
The use of microorganisms having a nitrilasic activity for hydrolyzing acrylonitrile or methacrylonitrile (hereinafter simply referred to as (meth)acrylonitrile) to produce acrylamide or methacrylamide (hereinafter simply referred to as (meth)acrylamide) has been known. Such a process is described in U.S. Pat. No. 4,001,081. As such microorganisms, bacteria of the genera Bacillus, Bacteridium in the sense of Prevot, Micrococcus and Brevibacterium in the sense of Bergey, etc., have been used and the inventors have also used microorganisms belonging to the genera Corynebacterium and Nocardia, described in Japanese Patent Application (OPI) No. 129190/79.
In producing (meth)acrylamide from (meth)acrylonitrile using these microorganisms, cells of these microorganisms act on (meth)acrylonitrile directly or after immobilizing them with polyacrylamide gel, etc. in an aqueous medium (for example, water, physicological saline, buffer solution, etc.). The reaction is usually conducted under the conditions of a substrate ((meth)acrylonitrile) concentration of about 1 to 10 wt%, a cell concentration of about 1 to 10 wt%, a pH of 7 to 9, at 25.degree. to 30.degree. C. for 0.5 to 10 hours so as to proceed the enzymatic reaction smoothly.
In the field of microbial reactions, batchwise or continuous column processes have recently been proposed using immobilized cells prepared by forming microbial cell particles which is advantageous from the point of view of the cell separation from a reaction solution, the availability of repeated use of the cells, and increasing enzyme stability. Such techniques are also useful in the process of producing (meth)acrylamide using microorganisms in the present invention.
However, a (meth)acrylamide aqueous solution produced using microorganisms is unstable and so susceptible to polymerization that concentration is difficult and, in addition, in a continuous column process, the (meth)acrylamide produced often polymerizes during hydrolysis which prevents smooth operation. The addition of known polymerization inhibitors such as methoxyquinone, copper salt, etc. might be considered but, with a (meth)acrylamide aqueous solution produced through microbial reaction, sufficient effects of the inhibitors cannot be attained unless these polymerization inhibitors are used in large amounts. Addition of such inhibitors in large amounts adversely affects the microbial reaction and seriously deteriorates the quality of the (meth)acrylamide aqueous solution.